1. Field of the Invention
The field of the present invention is the display of stereoscopic motion pictures, and more specifically to increasing image brightness in the projection of stereoscopic images.
2. Description of the Related Art
Stereographic moving images are frequently transmitted using projection systems, including but not limited to the ZScreen® product available from Real D and StereoGraphics® Corporation. A primary concern relating to stereoscopic image projection is the low brightness of the image on the screen. The ZScreen and other similar approaches employ at least one absorption sheet polarizer for stereoscopic image selection, and in case, the brightness of the image is reduced by at least fifty percent. In other words, the stereoscopic image is less than half the brightness of a projected planar image. Since analyzer polarizers are used for image selection, the final brightness results from the losses of two parallel axes polarizers giving considerably less than half the planar brightness.
One technique that has been employed to decrease the brightness loss due to projection using polarizer image selection is to use high gain projection screens. This method can partially mitigate the loss in brightness, but the fundamental light loss problem associated with absorption polarizers remains because sheet polarizers achieve their function by passing through light polarized along the polarizer's transmission axis and holding back the remainder of the light. The light held back heats the polarizer instead of providing useful illumination.
It is therefore beneficial to address and overcome the brightness issue present in previously known stereoscopic image selection techniques for projection, and to provide a stereoscopic projection apparatus or design having improved brightness over devices exhibiting the light loss described herein.